The number 81081
81081 is a composite number with 40 divisors. Its prime factorisation is × 7 × 11 × 13. Divisors (40): 1, 3, 7, 9, 11, 13, 21, 27, 33, 39, 63, 77, 81, 91, 99, 117 … 81081.
Pick any whole number from 1 to 100,000.
How to work it out
- 1
What is special about 81081: a happy number: repeatedly adding the squares of its digits reaches 1.
- 2
81081 is composite. Its prime factorisation is
- 3
The divisors add up to 162624; without 81081 itself that is 81543, so 81081 is abundant (81543 is more than 81081). Euler's totient φ(81081) = 38880 numbers up to 81081 share no factor with it.
- 4
The digits of 81081 add up to 18, and repeating that until one digit is left gives the digital root 9. The Collatz sequence (halve if even, else 3n+1) takes 89 steps to reach 1.
LaTeX source of the formulas on this page
\[ 81081 = 3^{4} \times 7 \times 11 \times 13 \]81081 at a glance
| Property | Value |
|---|---|
| Type | composite |
| Number of divisors | 40 |
| Sum of divisors | 162624 |
| Euler totient φ(n) | 38880 |
| Square | 6574128561 |
| Cube | 533036917854441 |
| Square root | 284.747256 (= 9√1001) |
| Digit sum / digital root | 18 / 9 |
| Collatz steps to 1 | 89 |
| Scientific notation | 8.1081 × |
81081 in other forms
| Form | Value |
|---|---|
| In words | eighty-one thousand and eighty-one |
| Binary (base 2) | 10011110010111001 |
| Octal (base 8) | 236271 |
| Hexadecimal (base 16) | 13CB9 |
| Base 3 | 11010020000 |
| As time | 81081 seconds = 22 h 31 min 21 s |
Is 81081 divisible by 2 to 12?
| Divisor | Answer | Rule |
|---|---|---|
| 2 | No (remainder 1) | A number is divisible by 2 if the last digit is even (0, 2, 4, 6, 8). |
| 3 | Yes (81081 ÷ 3 = 27027) | A number is divisible by 3 if the digits add up to a multiple of 3. |
| 4 | No (remainder 1) | A number is divisible by 4 if the last two digits make a multiple of 4. |
| 5 | No (remainder 1) | A number is divisible by 5 if the last digit is 0 or 5. |
| 6 | No (remainder 3) | A number is divisible by 6 if it is divisible by both 2 and 3. |
| 7 | Yes (81081 ÷ 7 = 11583) | A number is divisible by 7 if double the last digit and subtract it from the rest: the result is a multiple of 7. |
| 8 | No (remainder 1) | A number is divisible by 8 if the last three digits make a multiple of 8. |
| 9 | Yes (81081 ÷ 9 = 9009) | A number is divisible by 9 if the digits add up to a multiple of 9. |
| 10 | No (remainder 1) | A number is divisible by 10 if the last digit is 0. |
| 11 | Yes (81081 ÷ 11 = 7371) | A number is divisible by 11 if the alternating sum of the digits is a multiple of 11. |
| 12 | No (remainder 9) | A number is divisible by 12 if it is divisible by both 3 and 4. |
Questions
Is 81081 a prime number?
No. 81081 = × 7 × 11 × 13, so it is divisible by 3.
What are the factors of 81081?
1, 3, 7, 9, 11, 13, 21, 27, 33, 39, 63, 77, 81, 91, 99, 117, 143, 189, 231, 273, 297, 351, 429, 567, 693, 819, 891, 1001, 1053, 1287, 2079, 2457, 3003, 3861, 6237, 7371, 9009, 11583, 27027, 81081.
What is 81081 in binary?
10011110010111001 (hexadecimal 13CB9, octal 236271).
What is the square root of 81081?
About 284.7473, exactly 9√1001.
Is 81081 divisible by 3?
Yes. Its digits add up to 18, a multiple of 3.
What is special about the number 81081?
81081 is a happy number: repeatedly adding the squares of its digits reaches 1.